Take an image with an empty sample holder. If the image is not homogeneous and you see black or white dots (fig. B), this is a sign that the scintillator needs to be cleaned or that a gain reference needs to be redone.

Position yourself at 4000x and spread the beam over the entire screen by turning the illumination to the right.

Do Camera > Prepare Gain Reference. “Camera must be inserted now?” > Yes

“Remove the specimen from the field of view, spread and center the illumination so that it is large enough to evenly illuminate the CCD, and lift up the viewing screen to expose the camera if necessary.” > OK

“Any existing gain images will be overwritten. Is this OK?” > Yes

Images will be taken automatically. Normally a message asking to adjust the intensity so that the cursor is in the green region will appear: “Adjust the intensity so the center of the intensity indicator is in the green region.”. If you are not able to place the entire cursor in the region (fig. C), do Abort and start again with a more spread out beam (fig. D). Otherwise, Proceed.

You may have to repeat the intensity adjustment a few times during the process.

When it is finished, if we take an empty image, we should obtain something homogeneous (fig. A).